Automobile History

SUSPENSION

On a summer day in 1904 a young man by the name of
William Brush helped bring about the modern automobile suspension system. Driving
his brother Alanson's Crestmobile, Brush was rolling along too fast for the unpaved
roads of the day and went into a curve at 30 mph.
The car's right front wheel skittered onto the dirt shoulder and whammed into a deep
rut. Almost at once, the wheel started to shimmy violently. The undulations of the
jarred right front elliptic leaf spring had sent shock waves across the solid
I-beam axle to the left side of the vehicle. This set the entire front of the
car to vibrating furiously. Brush was caught unawares and lost control. The
car crashed through a barbed-wire fence, hit a ditch and overturned in a
cow pasture.

Several hours later young William 'fessed up to Alanson, whose demeanor switched
from stern to thoughtful, since he was trying to design a better car. That car,
dubbed the Brush Two-Seat Runabout, finally appeared in 1906. It featured a
revolutionary suspension system that incorporated two innovations never before
assembled together: front coil springs and devices at each wheel that dampened
spring bounce -- shock absorbers -- mounted on a flexible hickory axle.

Some European car makers had tried coil springs, with Gottlieb Daimler in Germany
being the leading exponent. However, most manufacturers stood fast with leaf
springs. They were less costly, and by simply adding leaves or changing the shape
from full elliptic to three-quarter or half elliptic, the spring could be made to
support varying weights.

Leaf springs in one form or another have been used since the Romans suspended a
two-wheeled vehicle called a Pilentum on elastic wooden poles. The first
steel spring put on a vehicle was a single flat plate installed on carriages by the
French in the 18th century.

The venerable leaf spring, which some manufacturers still use in rear suspensions
today, was invented by Obadiah Elliot of London in 1804. He simply piled one steel
plate on top of another, pinned them together and shackled each end to a carriage.

The coil spring is not a spring chicken, either. The first patent for such a spring
(British patent No. 792) was issued to R. Tredwell in 1763. The main advantage of
coil springs was that they did not have to be spread apart and lubricated
periodically to keep them from squeaking, as leaf springs did.

Model T Ford leaf spring

Henry Ford's 1908 Model T Ford featured old-fashioned leaf springs with a novel
twist -- he used only one spring at each axle, mounted transversely, instead of one
at each wheel. Ford's adaptation of high-strength vanadium steel from a French
racing car allowed him to save weight and cut costs in many areas of the Model T
without compromising its durability.

With the exception of a car here and there, independent coil spring front suspension
remained in limbo for 25 years after the introduction of the Brush Runabout. Then
suddenly in 1934, General Motors, Chrysler, Hudson, and others reintroduced coil
spring front suspension, this time with each wheel sprung independently. In that
year, most cars started using hydraulic shock absorbers and balloon (low-pressure)
tires. Coupling a solid front axle with shock absorbers and these tires really
aggravated front end shimmy. Suspending each wheel individually lessened the
effects of spring bounce.

Not all cars used coil springs at first. Some had independently suspended leaf
springs. But soon after World War II, all manufacturers switched to coil springs
for the front wheels.

Buick became the first U.S. manufacturer to use back-end coil springs in 1938.
Manufacturers have switched back and forth from model to model between leaf and coil
springs since then. Generally, large, heavy cars are equipped with leaf springs,
while small light cars have coil springs.

Independent rear suspension became popular on the rough, twisty roads of Europe
because it can offer improved ride and handling. The cheapest method is the swing
axle, for which early VWs were infamous. The differential is bolted to the frame,
with constant-velocity joints on each side. However, as the wheels bounce over
bumps, the tire camber and rear track change radically, causing some handling
quirks. In extreme maneuvers, an outside wheel can actually tuck under the car,
causing it to flip.

Axles with joints at both ends do a better job of keeping the wheels upright in a
turn, and an amazing variety of control arms have been used to meet this end.
Trailing arms, once popular, sometimes allowed trailing throttle oversteer -- lift
your foot off the gas pedal in a turn and the rear wheels shift slightly, throwing
the car into a skid. Modern designs use up to six control links at each wheel to
prevent such erratic behavior as bump steer and trailing throttle oversteer.

Air suspension, which Lincoln ballyhooed for some models in 1984 was introduced in
1909 by the Cowey Motor Works of Great Britain. It did not work well because it
leaked.

Stout-Scarab

The first practical air suspension was developed by Firestone in 1933 for an
experimental car called the Stout-Scarab. This was a rear-engined vehicle that used
four rubberized bellows in place of conventional springs. Air was supplied by small
compressors attached to each bellow. As you might imagine, the air bag suspension
was an expensive setup -- still is, in fact.

The first automobile to use torsion bar suspension was the 1921 Leyland. Most of the
credit for the wide acceptance of torsion bars in Europe goes to Dr. Ferdinand
Porsche who made it standard on most of his cars, beginning with the 1933
Volkswagen prototypes. By 1954, 21 makes of European cars were equipped with torsion
bars.

By contrast, in America, only Chrysler went the torsion bar route on its
large-sized cars. Despite its excellent ride qualities, high cost has limited its
acceptance in this country.

A renowned British surgeon, who had been knighted by Queen Victoria, was convinced
of a direct relationship between sound health and driving a car. Dr. William
Thomson's observations were made in a 1901 edition of the Journal of
Medicine where he stated:

I have found my drives to improve my general health. The jolting which occurs
when a motor car is driven at fair speed conduces to healthy agitation that acts
on the liver. This aids the peristaltic movements of the bowels and promotes the
performance of their functions.

Manufacturers of cars either did not read Sir Thomas's report or did not care for
his views, because soon afterward they began using shock absorbers to suppress
vehicular jolting.

Since early motor cars were limited to much the same speed as carriages, leaf
springs for them could be made of the right proportion to provide relatively
jolt-free rides. As roads were improved and speeds shot up, a 1909 edition of
Automobile Engineering noted:

When springs are made sufficiently stiff to carry the load properly over the small
inequalities of ordinary roads, they are too stiff to respond readily to the larger
bumps. The result is a shock, or jounce, to the passengers. When the springs are
made lighter and more flexible in order to minimize the larger shocks, the smaller
ones have too large an influence, thus keeping the [car] body and its passengers in
motion all the time. These two contradictory conditions have created the field for
the shock absorber.

The first shock

The first recorded use of a crude shock absorber is the
invention by one A. Gimmig in 1897. He attached rubber blocks to the top of each
leaf spring. When the suspension was compressed sufficiently, the rubber bumpers
hit bolts that were attached to the frame. Rubber bump stops are still used in many
modern suspensions, but their effect on ride control is minimal.

The first true shock absorbers were fitted to a racing bicycle in 1898 by a
Frenchman named J. M. M. Truffault. The front fork was suspended on springs, and
incorporated a friction device that kept the bike from oscillating constantly. In
1899, an American automobile enthusiast named Edward V. Hartford saw one of
Truffault's bikes win a marathon race at Versailles. Hartford immediately recognized
the automotive potential of the friction device.

Hartford and Truffault got together and by the next year Hartford had outfitted an
Oldsmobile with a variation of Truffault's device. This first automobile shock
absorber consisted of a pair of levers that were hinged together with a pad of
rubber placed at the pivot point. One of the lever arms was attached to the frame,
while the other was bolted to the leaf spring.

A bolt placed at the hinge point could be tightened or loosened to increase or
decrease the friction, providing a stiffer or softer ride. The Truffault-Hartford
unit was, therefore, not only the first automotive shock absorber, but also the
first adjustable shock.

Hartford brought the car to America, where he opened his own plant, the Hartford
Suspension Co., in Jersey City, New Jersey. His first big contract came from Alanson
P. Brush, who installed shock absorbers along with front coil springs on the 1906
Brush Runabout. The ride given by the car was called "magnificent" in a critique
written by Hugh Dolnar for Cycle and Automobile Trade Journal.

From then on shock absorber designs came fast and furious.

Gabriel Snubbers

This consisted of a housing that contained a belt
wound into a coil. It was kept under tension by a spring. The housing was
fastened to the frame and the outer end of the belt was attached to the axle to
limit the degree of rebound from a jolt.

The Gabriel Co. started operation in 1906 making accessory auto horns. The
founder, Claude H. Foster, named his firm after the horn-tooting angel Gabriel.
When the pushbutton horn came along in 1914, it killed the Gabriel and all other
body-mounted horns. Foster looked for a product to keep his company in business
and came across the Snubber.

Equalizing springs

These were auxiliary coil springs used in addition to
the leaf spring. Since each spring had a different harmonic frequency, they tended
to cancel out one another's oscillations. But they also added to ride harshness
and soon fell out of favor.

Air springs

Air springs combine spring and shock absorbing action in one
unit and were often used without metal springs. The first one was developed by
Cowey Motor Works of Great Britain in 1909. It was a cylinder that could be filled
with air from a bicycle pump through a valve in the upper part of the housing. The
lower half of the cylinder contained a diaphragm made of rubber and cord which,
because it was surrounded by air, acted like a pneumatic tire. Its main problem
was that it often lost air.

The newest air spring, developed by Goodyear, is found on some late-model
Lincolns. Like the ones that have preceded them, these ride-on-air units are more
costly than conventional springs and hydraulic shock absorbers.

Hydraulic shock absorbers

M. Houdaille of France gets credit for
designing the first workable hydraulic shock absorber in 1908. Hydraulic shocks
damp spring oscillations by forcing fluid through small passages. In the popular
tubular shock, a piston with small orifices is attached to the chassis and a
cylindrical oil reservoir is attached to the suspension or axle. As the suspension
moves up and down, the piston is forced through the oil, resisting the action of
the spring.

One-way valves allow different orifices to be used to control suspension jounce
and rebound. This is called a double-acting shock. The latest wrinkle is to add a
chamber of compressible gas at one end of the fluid reservoir to cushion the
damping action.

Monroe built the first original equipment hydraulic shocks for Hudson in 1933. By
the late 1930s the double-acting tubular shock absorber became common on cars made
in the United States. In Europe, lever-type hydraulic shocks prevailed into the
'60s. They resembled the Hartford friction shock, but used hydraulic fluid instead
of a friction pad.

MacPherson struts

With the advent of front-wheel-drive cars, manufacturers in the 1970s and '80s
started using MacPherson struts. MacPherson, a GM engineer, developed this unit in
the 1960s. It combines the coil spring, hydraulic shock absorber, and upper
suspension arm into a single compact device. The main advantage is that it allows
the necessary space for positioning the front-drive transaxle.

Several Japanese cars now feature struts with shock valving that can be adjusted
from soft to firm by electric motors while the car is moving. The driver has a
choice of three settings, but a signal from the speedometer usually overrides the
manual control at highway speeds to set the shocks on firm.

The Nissan Maxima for 1985 sold in Japan had electronically controlled shocks that
automatically provided a soft, medium, or firm ride depending upon road conditions,
speed, and driving style. A sonar unit under the bumper monitored the road surface,
while other sensors checked speed, acceleration, steering angle, and brake use.

Data were fed to a central processing unit that decided if you were driving gently
or aggressively, then activated shafts in the shock absorbers that altered the size
of fluid passages.

The Lotus Active Suspension System does away with springs and shock absorbers
altogether. Eighteen motion sensing transducers send data to four
computer-controlled hydraulic rams. The system distinguishes roll, dive, jounce, and
bump. Valves in the rams adjust the ride accordingly. These valves can change
position as much as 250 times per second.

The Lotus system has the uncanny ability to keep a car level in a tight turn
or even bank it toward the inside of the turn, rather than leaning to the
outside as other cars do.